Whales that live and hunt in the deeper, darker parts of the ocean use what people commonly call “whale songs” for more than just mating and communication, but also use echolocation to find their next meal. New research performed in eastern North Carolina shows the increasing number of plastics in the world’s seas may be causing cetaceans to eat things that are harmful.
Deep-diving whales, like sperm whales, pygmy sperm whales and goose-beaked whales, send out clicks and buzzes from a vocal cord-like structure near their blowholes, and Duke University graduate student Greg Merrill said the sound that bounces back tells them if there is some tasty squid or jellyfish nearby to snack on.
“The study we did looked at deep diving toothed whales in particular, so, animals that forged deep in the ocean where there is no light. So, instead of eyesight they're using echolocation," he explained. "They emit a sound from the top of their head, it hits an object, presumably food, and then it bounces back to their lower jaw and then travels up to their inner ear where they can interpret that sound and determine where their prey was.”
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Merrill led the research into whether ocean plastic trash -- which is routinely found in the guts of stranded whales – was confusing the whales into thinking the garbage was food.
“Their stomachs often have large pieces of plastic in them and those are commonly balloons, plastic grocery bags, milk jugs, oil jugs, things like that," he said.
So, he gathered trash from along the shorelines in Beaufort and Atlantic Beach, as well as some squid and squid parts found in the stomach of a whale that died on the Outer Banks, to map their sonar signals. The trash and the squid were put under the sonar transponder on the Duke Marine Lab's ship R/V Shearwater to test them.
Merrill said, "We strung those up and hit them with the echo sounder as well to try and you know as a proxy to get an idea of even though it wasn't the whole body of the animal we knew that those came directly from an animal that the whales were eating.”
Merrill said the sound that bounced back may indicate, to the whale, that a squishy morsel is just ahead – that squid or jellyfish – but plastic debris floating in the water sounds to them very much the same.
“That the sound that bounces back is pretty similar to that of plastic marine debris as it is to the same types of food that they're eating," he said.
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Swallowed plastic trash can have a devastating impact on the magnificent ocean-going mammals. Almost exactly one year ago, a live Gervais' Beaked Whale washed up in Emerald Isle and died soon after, and a necropsy found the female calf died from eating a plastic or mylar balloon.
"They do two main things; they can block the stomach so actual food can't really be digested very well or they start to impact the stomach so they can't really pass through the rest of the stomach into the intestine and out the animal," Merrill said, "So, the stomach starts to get fuller and fuller, and they have this false sense of being full. So, they'll stop eating but they don't actually have food in their stomach so they start starving.”
And Merrill added that the harder plastics that are increasingly found in the sea can also cause other harms. He said, “The rigid plastics like bottles, they can fragment and be kind of sharp and they'll scar or tear the stomach, as well which can cause infections and internal bleeding, so eventually all of this can lead to death which is really pretty sad.”
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While there are some uses for plastics that make sense, he said wrappers and plastic shopping bags and other single-use plastics are detrimental to the environment.
"There are a lot of good uses for plastic, like in the medical field for sterility reasons and preventing infection," he said, "We use disposable items and those are often plastic and that I think is an excellent use for them.”
But Merrill said plastic is, "Made of all kinds of chemicals that make it toxic as well so it's a really complicated, complex issue. Single use plastic items packaging are just completely unnecessary in a lot of cases, so, I think policy changes are really important to help reduce that.”
He’s urging people to write to their U.S. lawmakers, asking them to put policies in place that would reduce the amount of single-use plastics that is used, and could make its way into our oceans and other sensitive environments.
The organization Oceana found records of almost 1,800 animals from 40 different species swallowing plastic or becoming entangled between 2009 and 2019.
